Organic semiconductors exhibiting complementary-type carrier mobility are the key components for the development of the field of “plastic electronics”. We present here a novel series of αω- and isomerically pure β,β'-diperfluorohexyl-substituted thiophene and study the impact of fluoroalkyl substitution and conjugation length vìs-à-vìs the corresponding fluorinefree analogues. Trends between the fluorinated and fluorine-free families in molecular packing, HOMO-LUMO gap, and π-π interactions are found to be strikingly similar. TFT measurements indicate that all members of the fluorinated series are n-type semiconductors

The properties of thin film transistors (TFT's) on plastic substrates with active silicon films deposited by microwave ECR-CVD were studied. Two types of plastic were used, PEEK and polyimide. The a-Si:H TFT deposited at 200°C on polyimide substrates showed a saturation field effect mobility of 4.5 cm2/V-s, a threshold voltage of 3.7 V, a subthreshold swing of 0.69 V/dec and an ON/OFF current ratio of 7.9×106, while the TFT fabricated on PEEK at 200°C showed a saturation field effect mobility of 3.9 cm2/V-s, a threshold voltage of 4.1 V, a subthreshold swing of 0.73 V/dec and an ON/OFF current ratio of 4×106. Comparison is made to TFT's with the Si deposited at 400°C on glass.

The optical degradation of polysilane copolymer has been studied in spin cast thin films and solutions using light source of 325 nm wavelength. The room temperature photoluminescence (PL) spectrum of these films show a sharp emission at 368 nm when excited with a source of 325 nm. However, the PL intensity deteriorates with time upon light exposure. Further the causes of this degradation have been examined by characterizing the material for its transmission behaviour and changes occurring in molecular weight as analysed by GPC data.

An ultra-low temperature processed silicon dioxide film has been fabricated by inductively coupled plasma chemical vapor deposition at 150°C using He/N2O/SiH4 mixture. The deposited silicon dioxide film exhibits a high breakdown field larger than 6MV/cm in case of high ICP plasma condition while the flat band voltage of the oxide film significantly shifted in the negative direction with increasing ICP power. In order to obtain both high electrical breakdown filed and the low flat-band voltage, excimer laser irradiation with the energy density of 430mJ/cm2 is employed. The oxide film irradiated by excimer laser exhibited considerably shifted in the positive direction without scarifying the breakdown characteristics.

Organic semiconducting polymers are an attractive alternative to conventional inorganic materials because of the ability to process the polymers from solution and apply them to flexible substrates using lower temperatures and at a lower cost. Direct writing of these materials has the potential to reduce processing steps and material waste. While printing of semiconductors for organic light emitting diodes (OLEDs) is well known, little has been reported on printing semiconductors for organic thin-film transistors (OTFTs). We have developed a process to fabricate TFTs and arrays using jet printing to eliminate all photolithographic patterning. Active layers of the polymeric semiconductor are jet-printed for the active layer. Many factors are found to affect the characteristics of devices having a jet-printed semiconductor layer, including the substrate temperature, surface energy, device geometry, and drop size and overlap. We will discuss the printing conditions that lead to performance similar to that of devices fabricated by spin coating.

This article describes the properties of transistors that use organic semiconductors deposited on top of conducting polymer electrodes patterned by thermal transfer printing onto thin plastic sheets. The polymer, dinonylnaphthalene sulfonic acid doped polyaniline (DNNSA-PANI), contains several weight percent of single walled carbon nanotubes (SWNT) to improve its conductivity. Pentacene serves as the p-type organic semiconductor. The good electrical performance of these devices derives directly from the low resistance contacts between the printed DNNSA-PANI/SWNT source/drain electrodes and the pentacene. The measurements presented here quantify the behavior of these contacts and provide some morphological evidence for their low resistance. The excellent characteristics of the transistors and the operational flexibility of the thermal transfer printing technique that is used to pattern them represent results that may be an important step for the development of means to build realistic flexible electronic devices.

In this work we present fully patterned organic transistors based on selective electropolymerization of conducting polymers that enables simple fabrication of micron scale features. It involves fabrication of pentacene field effect transistors in which the conducting, insulating parts as well as the substrate are all made of polymers. We have fabricated drain and source electrodes by electropolymerization of 3,4- ethylenedioxythiophene and gate by spin coating of commercially available poly( 3,4- ethylenedioxythiophene) (PEDOT:PSS) aqueous dispersion, polyvinylalcohol for the gate dielectric layer, and pentacene for the organic active layer. We have built a top-gate structure with gate dielectric layer and gate placed on the top of the pentacene layer, and in a such way obtained protection of the active layer could permit enhancement of the operating time of devices. Carrier mobility as large as 0,01 cm2/V s was measured. Functional all- organic transistors have been realised using a simple and potentially inexpensive technology.

An ultra-low temperature (< 200°C) polycrystalline silicon (poly-Si) film is fabricated for the plastic substrate application using inductively coupled plasma chemical vapor deposition (ICP-CVD) and excimer laser annealing. The precursor active layer is deposited using the SiH4/He mixture at 150°C (substrate). The deposited silicon film consists of crystalline component as well as hydrogenated amorphous component. The hydrogen content in the precursor layer is less than 5 at%. The grain size of the precursor active silicon film is about 200nm and it is increased up to 500nm after excimer laser irradiation.

In recent years, there has been an increased interest in the use of flexible substrates in microelectronic fabrication. Flexible substrates, such as polymers and metals have the potential to be utilized in roll-to-roll processing, resulting in low cost, rugged systems. Thin flexible stainless steel foils offer a number of advantages over polymers for device and circuit fabrication, most significantly in the increased thermal budget tolerance that they provide. This enables the utilization of high temperature processes in the fabrication and the production of high performance devices and circuits.

Thin film transistors have been fabricated on thin stainless steel foils using a variety of crystallization and gate dielectric approaches. N-channel devices with average effective mobility values of 250cm2/Vs and p-channel devices with effective mobility values in the region of 90cm2/Vs were successfully fabricated. Both digital and analog circuits, such as operational amplifiers, ring oscillators and a variety of shift register designs were also fabricated, and their basic performance characteristics will be presented in this paper. The characteristics of ring oscillators having 19 inverter stages operating with speeds of 15MHz or higher, along with the characteristics of various shift register architectures with maximum operating frequencies above 1MHz, will be reported. The impact of process and design parameters on their operation was evaluated and will be addressed in this paper.

The results that are presented in this paper constitute the first successful implementation of high performance circuitry having a high degree of scalability and complexity on thin metal foils, thus making the fabrication of efficient, inexpensive and versatile systems on flexible foils for a large variety of applications a realistic prospect.

According to the situation recognition of a basic limit of electronics expansion in silicon planar technology, one proposal based on a new technology completely different from planar structure is done here. The new concept of the technology is “textile structure” for integrated optoelectronic circuit. The background of the new concept is shown from some historical view point. The concept is also discussed as an opto-electronic united circuit and a “Clothes” level system from application-view point. Characteristics and elemental technology of the textile hybrid system are considered for future development of this concept. Several concrete compositions and characteristics of the proposed system are compared with those of present technology to construct a new electronics system. This proposal is also discussed in flexible electronics concept.

The aim of this research is to develop low temperature gate dielectric/passivation layer for μc-Si and poly-Si based devices and circuits compatible with plastic substrates.

The PECVD silicon oxide films were fabricated from mixture of silane and nitrous oxide at 250 °C, 120 °C and 75 °C. Helium, argon and nitrogen were used as diluent gases to optimize density, stress, uniformity, and electronic properties.

Chemical composition and bonding in the films were studied by FTIR spectroscopy. The absorption peak at 1075-1080 cm-1 observed in the spectrum of each film corresponds to SiO2 stretching mode. No presence of SiH stretching or NH-stretching vibrations was found in the FTIR spectra of the samples.

Film uniformity was varied from 1.44 % to 5.60 % for 3“×3” area. Four wafers were processed at the same time. The deposited films have compressive stress varied from 0.063 GPa to 0.117 GPa. Respective film density is in the range from 1.63 g/cm3 to 1.77 g/cm3.

The electronic properties were studied on MOS capacitors with 200 nm thick SiOx. The dielectric permittivity was in the range between 2.03 and 3.57. The dielectric breakdown at 9 MV/cm was observed for the films deposited at 120 °C. The films deposited at higher temperatures are characterized by lower leakage current density, which was 3.7.10-10 A/cm2 for the sample deposited at 250 °C, 9.10-9 A/cm2 for 120 °C, and 2.2.10-8 A/cm2 for 75 °C at 5 MV/cm.

The a-Si:H based TFTs were fabricated using low temperature oxide as gate dielectric. TFTs demonstrate threshold voltage (3.02 – 4.12 V) and mobility (0.12 – 0.59 cm2/Vs) comparing with those using silicon nitride.

Transfer of monocrystalline silicon films to arbitrary foreign substrates is a promising way for the fabrication of high quality silicon films on foreign substrates, demonstrated by solar cell efficiencies on glass as high as 16.6 % in the past. Transfer technologies also enable the use of flexible substrates. This paper investigates the mechanical stability of the separation layer for two different morphologies. First measurements on the minimum bending radius of unsupported silicon films are presented that allow us to estimate minimum curvatures for flexible monocrystalline devices. Finally, we report the first flexible monocrystalline thin film silicon solar cell of 4 cm2 with an independently confirmed efficiency of 14.6 %.

In flexible electronics, plastic substrates can limit processing temperatures to less than 100° C. Consequently, most semiconductors, including amorphous silicon, may be incompatible with temperature-sensitive plastic substrates. While organic semiconductors may seem well suited to this particular application niche, their stability is questionable and their mobility is often low (∼0.1 cm2/V-s). In this paper we show that ZnO is a promising semiconductor candidate for flexible electronics, because thin film transistors can be fabricated at room temperature with higher mobility (> 1 cm2/V-s) and high on/off ratio (> 104).

The new integrated circuit concept that forms electronic equipment by the textile structure using the flexible fiber that has equipped the field effect transistor, the light emitting diode, the wiring pattern, etc. is proposed [1]. In this report, the structure of the filamentous body as a basic structure of the cloth with various electronic functions was examined. In order to simplify circuit composition, an active element such as field effect transistors, the electrode pattern for wiring, and the pads for connection are formed on the warp, and the electrode pattern for wiring and the pad for connection are formed on the woof. The circuit composition and a concrete structure of the warp and the woof are discussed.

Active matrix organic light emitting diode displays based on thin, flexible metal foil substrates offer a novel approach to fabricate light, flexible and rugged displays. Metal foils allows devices to be fabricated at higher process temperatures yielding better device characteristics than plastic substrates. Furthermore, the conductive nature of such substrates enables more efficient use of pixel area through the use of a global power electrode. We are implementing Active Matrix Organic Light Emitting Diode (AMOLED) displays on flexible stainless steel substrate using 2 TFT and 4 TFT pixel circuit topologies with two different layout realizations that exploit the conductive properties of the substrate.

The field of organic light emitting diodes (OLEDs) has matured considerably within recent years and first products are commercially available. After a brief review of the improvement of individual OLEDs we will focus on research topics for the preparation of passive matrix (PMOLED), active matrix (AMOLED) and full color displays. To date, the properties of organic matrix displays basically meet consumer product requirements. Anyhow an industrial cheap fabrication technology for reliable displays is not established yet. To meet the industrial demands for device fabrication a new horizontal in-line vacuum system for a massproduction compatible device manufacturing was installed. For material saving large area coatings the system accommodates up to 7” × 13” substrates. Different PMOLED-Displays based on vacuum deposited organic compounds have been prepared by various fabrication techniques. We demonstrate a 2 inch organic display with 24 × 32 single pixels and 0.9 × 0.9 mm2 pitch whereby cathode texture was achieved using photoresist barriers featuring a distinct undercut. Due to the inherent limitations of multiplexing and in order to satisfy the need for large area, high resolution displays the basic concepts for an active matrix addressing scheme are dealt with. In this regard transparent and electrically inverted top-side emitting diodes (IOLEDs) will be demonstrated. The latter are advantageous for the incorporation of powerful nchannel thin film transistors in the AMOLED driver backplanes. An all-organic smart pixel device comprising a single Pentacene based organic field effect transistor (OFET) and a conventional OLED was successfully prepared. Furthermore a new flash-sublimation technique for the spatially selective deposition of small organic molecules will be presented. We prepared OLEDs comprising flash-deposited Tris-(-8-hydroxyquinoline) aluminium (Alq3) and Alq3 doped with DCM2 which demonstrate the suitability of this technique for preparation of fullcolor displays based on small organic molecules.

A variety of polymer materials including polyimide (PI), polyarylate (PAR), polynorbonene (PNB) and polyethersulphone (PES) have been studied for use as substrates in the formation of active matrix displays based upon polycrystalline silicon (poly-Si) thin film transistors (TFTs). A process used to fabricate transflective mobile phone displays at 250°C on such substrates is described in detail. The NMOS TFTs show a mobility of 100cm2/Vs, and a threshold voltage of 3.9V; the PMOS devices have a mobility of 52cm2/Vs, and a threshold voltage of -6V. Issues relating to performance of these devices, yield of the arrays, and manufacturability are discussed.

In order to simultaneously decrease the production costs of thin film silicon solar cells and obtain higher performances, the authors have studied the possibility to increase the light trapping effect within thin film silicon solar cells deposited on flexible plastic substrates. In this context, different nano-structure shapes useable for the back contacts of amorphous silicon solar cells on plastic substrates have been investigated: random textures and gratings.

The optimisation of such back reflectors is so far empirical. Gratings constitute a well-known optical technique and their light trapping effect can be optimised by simulation.

A first conclusion is that neither the traditional “Haze factor” determined in air for a wavelength of 650nm nor the “rms roughness” of the surfaces are sufficient as criteria to optimise the back contact roughness for light trapping in cells. The shape of grains is a further essential criterion. The authors have so far obtained a relative current enhancement of 16% for solar cells deposited on randomly textured polyethylene terephthalate (PET) as compared to a corresponding conventional solar cell co-deposited on a flat mirror (Ag) on glass. Solar cells on PET with 6.3% stabilized efficiency have until now been obtained. Theoretical calculations indicate that gratings can enhance the current of a-Si solar cells by up to 30 percent.

Three-dimensional integrated circuits is a new and exciting field that has been spurred on by the need for conformal displays and detector arrays. These circuits are fabricated by interconnecting rigid sub-circuit islands made on a flat, deformable substrate. To prepare for interconnects, we apply a patterned deformable sacrificial material over the flat substrate. We then deform the substrate, with the sub-circuit islands and the sacrificial pattern on it, to a spherical surface. Following deformation, we evaporate interconnect metal and then liftoff the sacrificial material, leaving only the metal lines that interconnect the islands. The maximum size for a circuit island to remain intact is proportional to the island's thickness. The larger the island has to be, the thicker it must be made to prevent it from cracking. For 50 μm thick Kapton E substrates, it was found that 40 μm square SiNx islandsmust be at least 0.5 μm thick.With such thick islands, sidewall coverage during evaporation of the interconnect metal becomes difficult because of the dome shape of the substrate. Moreover, during substrate deformation, there is delamination that occurs at the island-substrate interface. This delamination forms a gap between the edge of the island, and the substrate. Thick metalization that covers both sidewall and islandsubstrate gap, produces a yield of 97% for 10 micrometer wide aluminum lines.

3-D displays, sensor skins, mechatronic structures, and e-textiles will rely on deformable and stretchable electronic circuits. It is likely that such circuits will be made of rigid semiconductor islands interconnected with one-time deformable or even elastic metallization. However, free-standing metal films fracture at tensile strains in the order of one percent, well short of the approximately ten-percent extension needed for deformable circuits. We have discovered that flat metal lines made on an elastomeric substrate can be stretched reversibly by ten percent without losing electrical conduction. While this phenomenon of “super-elastic” conductive films is as of yet unexplained, it appears to originate in the diversion of mechanical strain around cracks in the film and through the elastomer substrate. We fabricated 1mm thick poly-dimethylsiloxane (PDMS) membranes with up to 50-nm thick, 1-mm wide gold lines deposited by electron beam evaporation. Then we evaluated the structure of the gold films by optical and scanning electron microscopy, and measured the electro-mechanical characteristics in a strain tester, with contact electrodes applied to the film. We find that 50 nm thick lines retain their electrical conduction up to 30 percent strain. Also, when the tensile strain is cycled between 0 and 10 percent, the electrical resistance in the stressed and relaxed states are reproducible. We will describe substrate and conductor preparation, and their structural and electro-mechanical properties.